@jc235: "The County, having changed its speed policy early this year, is to 
consult on introducing trial 20mph zones, one per district.
Girton will be proposed zone for SCambs, and I couldn't possibly comment 
on the City one, which should be in the papers for CityAJC on 20 July 
(papers out on Friday).
The criteria is high levels of ped/cycle accidents and current speeds 
meeting criteria (average currently around or less that 24mph)
This is in addition to the proposed City Centre 20 mph which will be 
roads within innner ring (well nearly all...)
All we need now is for police to enforce them.
Jim Chisholm"
    @usenet: "On Tue, 07 Jul 2009 13:41:01 +0100, J. Chisholm put finger to keyboard
and typed:
<quote>
I don't quite understand the rationale here. If there is a high number
of accidents, and yet speeds are already low, then speed almost
certainly isn't the issue. It's far more likely that the problem is
poor road design and/or excessive traffic. Reducing the speed limit so
that people can't go any faster than they're already going (since the
ACPO guideline for enforcement is 2% + 2mph, a 20mph legal limit means
a practical limit of 24mph) isn't going to make any difference to
either of those.
Mark
Blog: <url>
Stuff: <url>"
    @mrc7ct: "In message <email_address>
<quote>
It is possible for average speeds to be low but for the accidents to
result from the proportion of traffic that is still travelling much
faster than the average. It isn't only the average speed that is
important but also the distribution of speeds on either side of the
average.
Mike
 o/ \\    //        |\   ,_ o      Mike Clark
<\__,\\  //   __o   | \ /  /\,   "A mountain climbing, cycling, skiing,
 ">    ||   _`\<,_  |__\  \> | caving, antibody engineer and
  `    ||  (_)/ (_) |   \corn computer user""
    @mrc7ct: "In message <email_address>
<quote>
But what if it is those travelling at 25-35mph in a 30mph limit
(and where the average is 24mph) that are mainly causing the problem? In
such a situation enforcing the speed limit won't help, but reducing it
and enforcing the lower limit might.
Mike
 o/ \\    //        |\   ,_ o      Mike Clark
<\__,\\  //   __o   | \ /  /\,   "A mountain climbing, cycling, skiing,
 ">    ||   _`\<,_  |__\  \> | caving, antibody engineer and
  `    ||  (_)/ (_) |   \corn computer user""
    @jc235: "<quote>
Yes
That is not a 'zone'.  A zone within Cambridge is most likely to be an 
area within a set of roads where 30mph is likely to be the ruling limit 
for some time to come. Say all the roads between Histon Rd and 
Huntingdon Rd.
Jim"
    @junk: "@a7g2000yqk.googlegroups.com>, <email_address> says...
<quote>
But it does.  "Government research showed that 20 mph zones reduced the 
incidence of traffic accidents by 60% and cut child pedestrian and child 
cyclist accidents by 67%, while overall vehicle speeds fell by an 
average 9.3 mph (14.9 kph)."
<url>
And that is accidents, not outcomes.  Further at 20mph you have a 95% 
chance of survival dropping to 55% at 30mph and wrightjohn@example.com.
Tony
"The single biggest problem in communication is the illusion that it has 
taken place" 
George Bernard Shaw"
    @jc235: "<quote>
Appart from a few Neanderthals, some of who lurk here, there is a 
general change in public attitudes to speeding, just as there was to 
drink driving. The percentage of vehicles breaking the 30mph speed limit 
is much reduced from 5 years ago even on roads without cameras.
Soon we may have a continental attitude to speeds in residential areas, 
with children, and old people moving about our residential areas without 
fear.
Jim"
    @rosenstiel: "<quote>
Yes, as well as Sedley Taylor and Luard Roads. Both schemes are being 
funded by City Council area committees.
Colin Rosenstiel"
    @paulnospam: "<email_address> writes:
<quote>
Although I was a little disappointed that they didn't go for the more
ambitious scheme that would have prevented rat running."
    @usenet: "On Tue, 07 Jul 2009 15:27:28 +0100, Mike Clark put finger to keyboard
and typed:
<quote>
In an urban area, everyone travels at pretty much the same speed when
the roads are anything other than near-empty. You can't overtake, so
you just follow along in line.
It is possible that the high accident rate is primarily happening at
off-peak times when traffic is lighter and faster. But that would
itself be a very unusal situation, since the majority of incidents
involving pedestrians and cyclists take place during the day when the
roads are busier.
This is one of those situations where more information is needed -
it's not enough to know that the accident rate is higher than normal,
it also matters what the most common factors are in those accidents.
I'd be rather surprised if excessive speed was actually one of them.
Mark
Blog: <url>
Stuff: <url>"
    @usenet: "On Tue, 07 Jul 2009 17:26:34 +0100, J. Chisholm put finger to keyboard
and typed:
<quote>
FWIW, I'm generally in favour of 20mph limits in streets that are
primarily or exclusively residential in nature. But one of the
problems with a blanket imposition in urban areas is that the mixed
nature of many British city centres makes that impractical. In
somewhere like Milton Keyenes, which has a tree topology that
separates residential streets from through and connecting routes, it's
easy to impose a blanket limit on all residential streets as there are
virtually no houses on the connecting routes. But in historic cities
like Cambridge, that's generally only possible in the newer suburbs.
In the more central, and older, areas the topology is more of a mesh,
and it's hard to apply a lower limit to all residential streets
without also affecting significant connecting routes. If you leave
some roads with the higher limit then they'll tend to attract more
traffic, which could be counter-productive in terms of safety and the
environment, but if you impose the limit on connecting routes as well
then, paradoxically, you can end up creating new rat-runs as distance
becomes more significant at lower speeds - a diversion to save a
minute at an average of 30mph may not be worth it, but it may become
worth it to save 2 minutes at an average of 15mph.
Mark
Blog: <url>
Stuff: <url>"
    @junk: "<email_address>>, <email_address> says...
<quote>
he
d
der.fcgi?artid=3D1127572
There's plenty more supporting data.  For example when Hull City Council=20
introduced 20mph zones on a quarter of its roads three years ago it led=20
to a 74% reduction in the number of crashes involving child pedestrians,=20
and a 69% reduction in child cyclist crashes, compared with the three=20
years before the speed limit changed. The overall number of collisions=20
in Hull has been reduced by 56%, and there has been a 90% reduction in=20
serious or fatal injury collisions.
Also research by the National Centre for Social Research found that 74%=20
of people wanted 20mph limits in residential areas as did 72% of=20
drivers.
=20
Tony
"The single biggest problem in communication is the illusion that it has=20
taken place"=20
George Bernard Shaw"
    @chrisshore: ""Mark Goodge" <email_address> wrote in message 
news:<email_address>
<quote>
To my mind, this is the attitude which needs to change. Saving 2 minutes is
neither here not there and driver behaviour/mindset needs to change to
become more relaxed about that.
Chrsi"
    @usenet: "On Wed, 8 Jul 2009 09:52:44 +0100, Chris Shore put finger to keyboard
and typed:
<quote>
For a single journey, it doesn't matter much. But over multiple
journeys it adds up, and for professional drivers operating within
legally restricted driving hours it can be a significant factor over
the course of a working day.
The other problem with applying the lower limit to connecting routes
as well as solely residential streets is that it affects buses too,
which has knock-on effects for timetabling and can make public
transport less attractive. That's particularly the case if the lower
limit is accompanied by any street furniture intended to force speeds
down, as buses (like all larger vehicles) are disproportionately
affected by it - they are less able to nip through the gaps than cars.
Mark
Blog: <url>
Stuff: <url>"
    @junk: "<email_address> says...
<quote>
Usually IME the time saved is only saved from the time waiting in the 
next queue rather than on the journey time.  In addition, as has been 
demonstrated by variable speed limits, often lowering the speed limit 
actually improves traffic flow and transit times.  Scandinavian cities 
that trialled cars that could not exceed the speed limit found their 
journey times improved.
Tony
"The single biggest problem in communication is the illusion that it has 
taken place" 
George Bernard Shaw"
    @roland: "In message <email_address>, at 
12:32:19 on Wed, 8 Jul 2009, Mark Goodge 
<email_address> remarked:
<quote>
That's very much the case. And is amplified by traffic lights, where 
arriving 5 seconds too late means a stream of traffic from another road 
is inserted between you and your destination. So you get to the next set 
of lights even later, and so on.
Roland Perry"
    @john: "<quote>
<mode=bitchy and not entirely serious comment> Oh, I thought we were
talking about cars, not bikes. </mode>
 J"
    @malcolmnews2008: "<quote>
I wonder how navigation tools are taught to be more relaxed (I also
wonder in some parts of cambridge how i am expected to know the route
people think i should be using)"
    @junk: "<email_address> says...
<quote>
Its obvious innit?  It must have been cyclists driving those cars ;-)
Tony
"The single biggest problem in communication is the illusion that it has 
taken place" 
George Bernard Shaw"
    @usenet: "On Wed, 8 Jul 2009 13:42:27 +0100, Tony Raven put finger to keyboard
and typed:
<quote>
It can do, yes, particularly if it's combined with "green wave"
timings for traffic lights so that someone travelling at a constant
legal speed along the dominant route doesn't have to repeatedly stop
and start. But if lower speed limits result in more, rather than less,
stop-start traffic then they will increase journey times.
As I've said before, I'm not opposed to lower speed limits in
principle. But they're a tool which needs to be used appropriately
rather than being seen as a general panacea for urban roads. Many of
their claimed benefits are based on surveys conducted in places where
they were used appropriately; you can't simply extrapolate from that
and assume that you'll get equivalent results everywhere. Part of the
reason why sites are chosen for trials of new ideas like 20mph zones,
"naked streets" (which I also very much like in principle, but don't
think are suitable for general deployment), etc is because they are
the type of site which is expected to benefit from them. So the
trials, if successful, don't prove anything other than the fact that
they are, indeed, suitable for that type of location. 
Mark
Blog: <url>
Stuff: <url>"
    @junk: "<email_address> says...
<quote>
I think its more than can do.  I cycle all over central London (the CC 
zone so not heavy traffic in general).  My routes mean there can't be a 
green wave factor.  I very frequently see people rush to get past me and 
then I pass them again waiting at the next light or the one after.  Its 
rare that cars make faster progress than I do.
Tony
"The single biggest problem in communication is the illusion that it has 
taken place" 
George Bernard Shaw"
    @ehk20: "<quote>
The traffic which inserts itself while you are waiting at the lights 
doesn't necessarily have much effect on the speed at which you can 
travel between the lights. If it moves at the same average speed as the 
traffic you are already with your delay is the traffic light, not the 
extra cars ahead of you."
    @ehk20: "<quote>
For what it is worth the 30Kph zones where I have experience them are 
either implemented in areas with few traffic lights, or where traffic 
lights are removed as part of the traffic calming measures put in place."
    @roland: "In message <email_address>, at 
19:05:33 on Wed, 8 Jul 2009, Espen Koht <email_address> remarked:
<quote>
No, because if I was ahead of that convoy of traffic maybe I'd be able 
to get through the next lights as soon as I arrive there.
Now, I have an entire "one light's worth" of traffic ahead of me that 
will steal an entire "one light's worth" of throughput for the next set 
of lights, meaning I am inevitably delayed by a whole cycle.
Roland Perry"
    @noone: "<quote>
It's probably a candidate precisely because it's a good, clear road and 
they'll be able to raise more revenue by sticking an unreasonably low speed 
limit on it and catching people exceeding it. Think of speed cameras and how 
many are actually in dangerous places and how many are purely for revenue 
collection.
Dave
da <email_address> (without the space)
So many gadgets, so little time."
    @ehk20: "<quote>
(Or maybe you will arrive just in time for the wrong part of the cycle). 
Anyway, "ahead of that convoy" assumes you didn't stop at that first 
light, whereas my point was that once you have stopped at that light, 
that is what will delay you, not cars entering the road ahead of you, 
assuming the speed of the traffic otherwise remains unchanged."
    @usenet: "On Wed, 08 Jul 2009 19:08:35 +0100, Espen Koht put finger to keyboard
and typed:
<quote>
Yes, that would make sense. With lower speeds, lights are less
necessary and removing them will improve the flow. That makes it a
win-win scenario, as the vehicle users get faster travel despite a
reduced maximum speed, while pedestrians and cyclists get the benefit
of improved safety.
Mark
Blog: <url>
Stuff: <url>"
    @whatever: ""Mark Goodge" <email_address> wrote in message 
news:<email_address>
<quote>
Aah if only this were true in Cambridge, the traffic engineers will state 
otherwise but you just go for a drive around town next xmas day, when v 
little other traffic is about and notice how many lights that are green as 
you approach, turn red and stop you, nothing else approaching any other 
direction..
It is an 'interesting' exercise and one the council denies happens, but 
please do try next xmas day and see for yourselves. "
    @roland: "In message <email_address>, at 
22:00:38 on Wed, 8 Jul 2009, Espen Koht <email_address> remarked:
<quote>
But if I arrive at the lights when red, I have some hope of getting 
through on the next cycle. But if there's a whole "one cycle-worth of 
convoy" between me and the next lights, I'll *never* be able to get 
through on the next cycle even if they go green just as the convoy 
arrives (I'll be the first one caught by the red at the end of the 
cycle).
It's the difference between arriving a few seconds earlier and being the 
last one through the lights; compared to being the first one who stops 
at the red and then suffers from the whole convoy being inserted between 
me and the next lights.
Roland Perry"
    @del2: "<quote>
Having been to the AJC meeting I can answer the question. Villages were 
scored on accident data and number of access points (you wouldn't 
believe the cost of a 20mph sign:-). Girton has 3 access points and 12 
accidents (9 slight, 3 serious). Only 2 other villages (Impington & 
Milton) have only 3 access points.
The discussion on the issue was disappointing to say the least. Officers 
had recommended the whole of Girton village for the experiment because 
they had no concept of what constitutes the village (eg a significant 
stretch of The Avenue leading to Madingley) The budget won't allow for 
any of the kinds of work which might encourage compliance (eg removal of 
road-markings)  or policing of course. Designed for failure, but the 
committee waved it through to the next stage and it will go out to 
consultation.
They have also approved a complete revision of the plans for Huntingdon 
Road: the 2m cycle lanes will now be 1.7m advisory lanes covered with 
red sludge and double yellow lines. All in all a miserable meeting.
Douglas de Lacey"
    @paulnospam: "Douglas de Lacey <email_address> writes:
<quote>
Yuck, and this is in the brave new world of a "Cycling Demonstration
Town"? What are we trying to demonstrate? How not to do it?"
    @noone: "<quote>
Landbeach and Rampton only have three access points, as far as I can tell. 
Perhaps they're remarkably accident-free in recent years and don't qualify. 
A quick look at Google Maps suggests that Girton has four: thee junctions 
with Huntingdon Road (Orchard Dr, Girton Rd and Thornton Rd) and the 
northern entry.
Dave
da <email_address> (without the space)
So many gadgets, so little time."
    @andrew_d_may: "<quote>
To what extent is Orchard Drive a public road? I have always seen it as 
a private road through the college.
Andrew"
    @del2: "<quote>
OK s/Orchard Drive/Whitehouse Lane :-) Oh, and add The Avenue. The point 
is that officers had no idea what constitutes "Girton". The bit they 
were thinking of only has 3 access points.
Landbeach and Rmpton didn't figure in the list of selected potential 
trial sites, conceivably on the basis of the accident stats.
I've been asked to discuss the issue on Radio Cambs some time between 8 
and 9 tomorrow morning.
Douglas de Lacey"
    @del2: "<quote>
17K, which has to include consultation, advertisement and (for all I 
know) legal fees. So yes, very small indeed; factored-in failure IMHO.
Yup.
Yup.
Yup. :-(
Douglas de Lacey"
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